Calc silicate gneiss - Harris
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Fact sheet
Description: 

This coarse-grained, calcite-rich, banded gneiss is from Sgarasta on South Harris in the Western Isles of Scotland. It was probably originally an altered volcanic rock in the Archean period. The rocks metamorphosed when subjected to high temperature and pressure during the Laxfordian orogeny, resulting in the coarse-grained rock.

The rock sample consists of bands rich in calcite, olivine (forsterite) and plagioclase. Also visible are bands rich in quartz, feldspar and amphibole. Calcite consistently shows deformation bands — often two sets of parallel bands are visible when viewed in plane polarised light and between crossed polars.

In Place
In Time
infoImage: 
Location description: 
Bagh Steinigidh, Sgarasta, South Harris, Western Isles, Scotland
Accuracy:
Location precision: 
Poor
Timescale:
Timescale: 
Archean
Ma = Millions of years ago
In Focus
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Type:
Type: 
metamorphic
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